Combined portable electric impact wrench and chipping hammer

ABSTRACT

A combined portable electric impact wrench and chipping hammer wherein the tool holder is movable axially by a pneumatic impeller which receives motion from the output shaft of an electric motor by way of a first transmission and a clutch which latter can be disengaged at the will of the user, and wherein the tool holder is rotatable by way of a multi-speed second transmission having a neutral position. By placing the second transmission in neutral position, the user can reciprocate the tool holder by way of the first transmission when the clutch is engaged. When the clutch is disengaged, the user can rotate the tool holder at one of several speeds by way of the second transmission. The second transmission can drive the tool holder at a selected speed while the clutch is engaged so that the tool holder moves axially and rotates about its axis. The second transmission embodies or is combined with a safety clutch which is disengaged when the tool holder offers excessive resistance to rotation.

United States Pa tent [191 Bleicher et al.

1111 3,828,863 51 Aug. 13, 1974 [54] COMBINED PORTABLE ELECTRIC3,720,269 3/1973 Wanner et al. 173/48 IMPACT WRENCH AND H N 3,774,69911/1973 Schuclt 173/48 HAMMER 3,789,993 2/1974 Jareck1.... 173/483,791,461 2/1974 Rosselet 173/48 [75] lnventorsi Manfred Bleicher,Leinfelden; Jorg al l pfl g i ar Primary Examiner-David H. Brown Kemnat;Germ)t Hansel Attorney, Agent, or Firm-Michael S. StrikerStuttgart-Plieningen; Wolfgang Schmid, Plattenhardt; Karl Wanner, [57]ABSTRACT Echterdmgen, all of Germany A C d Portable 16 p t h d om me e c1 ac wrenc an Asslgneei RllbertBoSch GmbH, Stuttgart, chipping hammerwherein the tool holder is movable Germany axially by a pneumaticimpeller which receives motion [22] Filed. July 6 1973 from the outputshaft of an electric motor by way of a first transmission and a clutchwhich latter can be dis- PP 376,935 engaged at the will of the user, andwherein the tool holder is rotatable by way of a multi-speed second [30]Foreign Application Priority Data transmission having a neutralposition. By placing the A 31 1972 G 2242944 second transmission inneutral pos1t1on, the user can "many reciprocate the tool holder by wayof the first transmission when the clutch is engaged. When the clutch[52] US. Cl 173/48, 173/109, 1177330111282, is disengaged the user canrotate the tool holder at one of several speeds by way of the secondtransmis- [511 i Eozd 7/02 Ezlb 5/00 E216 3/02 sion. The secondtransmission can drive the tool [58] Field of Search 173/48 47 holder ata selected speed while the clutch is engaged 'so that the tool holdermoves axially and rotates about [56] References Cited its axis. Thesecond transmission embodies or is com- UNITED STATES PATENTS bined witha safety clutch which is disengaged when 3,114,423 12/ 1 3 Na lun 17 /48X the tool holder offers excessive resistance to rotation.

3,463,246 8/1969 Bronnert... 173/47 3,507,337 4/1970 Chromy 173/48 x 26Claims, 7 Drawing Figures PArmmw -r 3.828.863

sum 1 or 5 Fig. 1

PAIENIEDAUBWB" f 3.828.863 sumu nrs I I Fig. 6

COMBINED PORTABLE ELECTRIC IMPACT WRENCH AND CHIPPING HAMMER BACKGROUNDOF THE INVENTION The present invention relates to portable power toolsin general, especially to electrically operated power tools, and moreparticularly to improvements in multiple-purpose portable power tools.Still more particularly, the invention relates to improvements inportable power tools of the type wherein a holder for a screwdriver,chisel, drill or another material removing or material penetrating toolis movable axially and is also rotatable about its axis.

A presently known combined portable impact wrench and chipping hammerwhich is disclosed in Swiss Pat. No. 507,066 comprises a tool holderwhich can receive axial impulses from a pneumatic impeller and can berotated at a single speed by way of a transmission which receives torquefrom the rotary output member of the prime mover. The transmission is astepdown transmission and the output shaft of the prime mover furtherserves to actuate the impeller. A drawback of the just described powertool is that the tool holder can only be rotated at a single speed andthat the impeller cannot be deactivated when the prime mover rotates itsoutput member. This limits the utility of the power tool, i.e., thelatter can be put to a very limited number of uses especially since itis not provided with means for permitting the attachment of a variety ofdifferently dimensioned material removing or material penetrating tools.

U.S. Pat. No. 3,500,696 discloses a portable electric drill wherein thetool holder cannot move axially but can be rotated at two differentspeed. The utility of this power tool is also limited due to the absenceof an impeller mechanism for the tool holder.

SUMMARY or THE INVENTION An object of the invention is to provide aportable power tool which is more versatile than presently knownportable power tools because it can be readily converted from use as animpact wrench or the like, to use as a chipping hammer or the like, orto use as a simple power drill or the like.

Another object of the invention is to provide a portable power tool ofthe just outlined character which can be converted from one type ofoperation to a selected other type of operation while in actual use,which can rotate a tool at several speeds, and which embodies novel andimproved safety features to prevent damage to its parts and/or an injuryto the user.

A further object of the invention is to provide novel and improved meansof transmitting motion from the prime mover to the axially movablerotary tool holder of a combined chipping hammer and impact wrench.

An additional object of the invention is to provide a portable powertool with a novel and improved multispeed transmission for rotating thetool holder.

Still another object of the invention is to provide a portable powertool with novel and improved control means for changing the speed ratioof and for deactivating the just outlined transmission.

The invention is embodied in a portable'power tool, particularly in acombined electric impact wrench and chipping hammer, which comprises ahousing, a prime mover (preferably an electric motor) mounted in thehousing and having a rotary output member, a tool LII holder which isrotatably and axially movably mounted in the housing and has'means forremovably supporting a chisel, drill or another material penetratingand/or removing tool, impeller means (preferably operating with acushion of compressed gaseous fluid) which is mounted in the housing andis actuatable to transmit to the tool holder recurring axial impluses,first transmission means which is mounted in the housing and has aninput element receiving torque from the output member of the primemover, a mobile output element for actuating the impeller means, andclutch means for moving the output element in response to rotation ofthe input element, first control means for disengaging the clutch meansat the will of the operator to thereby deactivate the impeller meanswhile the prime mover is free to rotate its output member, multi-speedsecond transmission means (preferably a two-sp eed gear transmission)mounted in the housing between the tool holder and the output member ofthe prime mover and having a plurality of different speed ratios and aneutral position, and second control means which is actuatableindependently of the first control means to select the speed ratio orthe neutral position of the second transmission means. This enables theoperator to cause the tool holder to move axially under the action ofthe impeller means while the second transmission means is in the neutralposition (i.e., while the tool holder'does not receive torque from thesecond transmission means) or while the second transmission means drivesthe tool holder at one of several speeds, or to disengage the clutchmeans of the first transmission means (so that the output element of thefirst transmission means is idle and fails to actuate the impellermeans) while the second transmission means rotates the tool holder at aselected speed.

It is further desirable to provide the power tool with a safety clutchwhich can form part of the second transmission means and serves todisconnect the prime mover from the tool holde when the latter offersexcessive resistance to rotation, even when the second control means hasbeen actuated by the operator to assume a position corresponding to oneof the several speed ratios of the second transmission means.

To novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved portable power tool itself, however, both as to itsconstruction and its mode of operation, together with additionalfeatures and advantages thereof, will be best understood upon perusal ofthe following detailed description of certain specific embodiments withreference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary longitudinalvertical sectional view of a portable power tool which embodies one formof the invention.

FIG. 2 is a sectional view as seen in the direction of arrows from theline II-II of FIG. 1;

FIG. 3 is a fragmentary sectional view as seen in the direction ofarrows from the line III-III of FIG. 2;

FIG. 4 is a fragmentary partly elevational and partly longitudinalvertical sectional view of a second portable power tool;

FIG. 5 is a fragmentary longitudinal vertical sectional view of a thirdpower tool;

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 1 to3, there is shown a spadehandle portable power tool which can be used asa chipping hammer and/or as an impact wrench. The housing of the powertool comprises a front section 1, a median section 2 and a rear section3 which latter is with a spade handle 3a (only partially shown). Thehousing sections 1,2 and 3 are separably connected to each other bymeans of suitable bolts, screws or analogous fasteners, not shown. Thelower portion of the median housing section 2 receives a prime moverhere shownas an electric motor 4 whose rotor 5 is connected with anoutput shaft 6 which is mounted in antifriction bearings providedtherefor in the front and median housing-sections 1 and 2. As shown inFIG. 1, the front end portion of the output shaft 6 is rotatable in afront antifriction bearing 7 having roller-shaped rolling elements andbeing located in front of a fly wheel 6a. The rear portion of the outputshaft 6 is rotatable in a rear antifriction bearing 8 having sphericalrolling elements. The rearmostportion of the output shaft 6 constitutesor is rigidly connected to a pinion or gear 9 which is in mesh with agear 11 secured to an intermediate shaft 10. The front end portion ofthe intermediate shaft 10 is rotatable in a first antifriction bearing10a which is mounted in an internal partition 2a of the section 2. Therear portion of the intermediate shaft 10 is rotatable in a secondantifriction bearing 1012 which is installed in a portion 3b of the rearhousing section 3. That portion of the intermediate shaft 10 whichextends between the front bearing 10a and the gear 11 carries a smallergear 12 and a larger gear 13. The gears 12 and 13 respectively mesh witha larger gear and a smaller gear 16 both rotatably mounted on a hollowshaft 14 which is rotatable in antifriction bearings 27 and 28 providedtherefor in the housing section 2. The gears 15 and 16 are immediatelyadjacent to each other and can be moved axially of the hollow shaft 14by a shifter fork 17 shown in FIGS. 2 and 3. The rear portion of thehollow shaft 14 is provided with an annulus of external torque receivingteeth 18 which can be moved into mesh with the internal torquetransmitting teeth of the gear 15 or with the internaltorquetransmitting teeth 21 of the gear 16. The space 19 between theinternal teeth 20 and 21 is wide enough to receive the external teeth 18when the multi-speed transmission including the gears 12, 13, 15, 16 andhollow shaft 14 is in neutral position. As shown'in FIG. 2, the sleeve14 is provided with four equidistant external torque receiving teeth 18.

The shifter fork 17 for the gears 15 and 16 is recipro cable along aguide rod 22 (shown in FIGS. 2 and 3) which is mounted in the housingsection 2, The means for moving the shifter fork 17 lengthwise of theguide rod 22 comprises a substantially rectangular leaf spring 23 havingtwo prongs 23a and 23b which flank an eccentric pin provided on acontrol shaft 24 having a portion extending from the housing section 2immediately adjacent to the housing section 3 and being pro- .vided witha handle 26. The handle 26 can be pivoted between three differentpositions including a lowerspeed setting of the multi-speedtransmission, a higherspeed setting, and the aforementioned neutralposition. As shown in FIG. 2, the shaft 24 extends substantially atright angles to a vertical portion or wall 2b of the intermediatehousing section 2. The parts 17 and 23-26 together constitute a controldevice which can be actuated by hand to select the speed and the neutralposition of the transmission 9-16.

The rear antifriction bearing 28 for the hollow shaft 14 comprisesroller-shaped rolling elements and the front antifiction bearing 27 forthe hollow shaft 14 comprises spherical rolling elements. The frontbearing 27 is immediately adjacent to the front housing section 1. Anintermediate portion of the hollow shaft 14 between the bearings 27 and28 is provided with several equidistant radially extending openings orcutouts 29 for spherical torque transmitting elements 30 forming part ofa safety clutch. The median portions of the torque transmitting elements30 are normally held in the respective opening 29 by a pressure ring 31which is biased forwardly by a strong helical spring 32 reacting againsta retainer 33 which abuts against an external shoulder of the hollowshaft 14 in front of the rear bearing 28. The front side of the pressurering 31 is provided with two mutually inclined outwardly and forwardlyflaring conical surfaces 34 and 34a. When the outermost portion of thespherical torque transmitting elements 30 are engaged by the innerconical surface 34, their innermost portions are caused to extendinwardly beyond the respective openings 29 so that they extend intoaxially parallel flutes 35 provided in a sleeve 36. The outer conicalsurface 34a of the pressure ring 31 tapers to a greater extent that theinner conical surface 34 (i.e., the conical surface 34a makes with theaxis of the hollow shaft 14 an acute angle which is larger than theactue angle between the axis of the shaft 14 and the inner conicalsurface 34) so that the surface 34a enables the torque transmittingelements 30 to move radially outwardly and to thereby abruptlydisconnect the sleeve 36 from the hollow shaft 14 in response to apredetermined resistance which the rotary and axially movable toolholder 37 of the power tool offers to rotation. The tool holder 37 has arearwardly extending portion or shank 37a provided with axially parallelexternal grooves or flutes 39 for portions of balls 38 which are mountedin radially extending openings of the sleeve 36. The balls 38 compel thesleeve 36 to rotate with the tool holder 37 or vice versa while theflutes 39 allow the shank 37a to move axially relative to the sleeve 36.The front portion of the tool holder 37 is provided with internalthreads 37b which can mesh with the external threads of a suitable toolT (see FIG. 4) such as a chisel, screwdriver or the like. A firstsealing ring 40 is interposed between the foremost portion of the sleeve36 and the front housing section 1. A second sealing element 41 isreceived in an internal groove of the sleeve 36 and engages theperipheral surface of the shank 37a. The foremost portion of the sleeve36 is further provided with a flange or collar 42 having an annulus ofteeth 43 separated by axially parallel grooves each of which can receivea projection 45 provided on a transverse blocking shaft 44 which isrotatably mounted in the front housing section 1. A portion of theblocking shaft 44 extends outwardly from the housing section 1 and isprovided with a handle (not shown) similar to the handle 26 of FIG. 2 toenable an operator to move the projection 45 into or from engagementwith the adjacent teeth 43 of the collar 42. When the projection 45engages the adjacent teeth 43, the sleeve 36 and the tool holder 7 areheld against rotation with the hollow shaft 14 of the multi-speedtransmission 9-16.

The multi-speed transmission 9-16 can rotate the tool holder 37 at twodifferent speeds. Furthermore, and as explained above, the handle 26 ofthe control device 17, 23-26 can be moved to a position corresponding tothe neutral position of the multi-speed transmission in which positionthe gears 15 and 16 can rotate relative to thehollow shaft 14 so thatthe tool holder 37 can be held by the projection 45 of the blockingshaft 44 against angular movement. The wall 21; of the housing section 2can be provided with indicia to facilitate the solution of a desiredposition for the handle 26. Analogous indicia (e.g., ON" and OFF can beprovided on the front housing section 1 adjacent to the handle for theblocking shaft 44.

THe power tool of FIGS. 1 to 3 further comprise a second transmissionserving to actuate at the will of the operator a pneumatic impellerwhich is installed in the hollow shaft 14 and is adapted to transmit tothe shank 37a of the tool holder 37 recurrent axial impulses in adirection to the left, as viewed in FIG. 1, to thereby drive the top ofa tool which is removably connected to the holder 37 by threads 37b intoa workpiece, such as a piece of concrete, wood, brick or the like. Theimpeller comprises a cylinder 61 which is movable axially in theinterior of the hollow shaft 14 and receives a piston or plunger 62which is adjacent to the rear end of the shank 37a. When the cylinder 61is caused to move forwardly, the cushion of compressed air in itschamber 61a urges the piston 62 forwardly and causes it to strikeagainst the rear end of the shank 37a.

The aforementioned transmissioned which serves to reciprocate thecylinder 61 of the impeller 61, 62 comprises an input element in theform of a bevel gear 46 which is secured to the intermediate shaft 10adjacent to the gear 11 and is in permanent mesh with a second bevelgear 48 mounted on a hollow clutch shaft 47. The shaft 47 is normal tothe intermediate shaft 10 and has radially extending opening 51' forspherical torque transmitting elements 51 portions of which extend intoaxially parallel internal grooves or recesses 52 of the bevel gear 48when the positive clutch including the hollow shaft 47, bevel gear 48and spherical elements 51 is engaged. Portions of the spherical elements51 are normally held in the grooves or recesses 52 by a conical shoulderof a displacing member or bolt 54 which is movable axially in the hollowshaft 47 between the illustrated operative position and an inoperativeposition and is biased to the operative position of FIG. 1 by a helicalspring 53 which reacts against an internal shoulder of the hollow shaft47. The control means for engaging or disengaging the positive clutchincluding the spherical elements 51 comprises a shaft 55 having aneccentric pin 56 which can move displacing member or bolt 54 upwardly,as viewed in FIG. 1, against the opposition of the spring 53 whereby thebolt 54 assumes its inoperative position and maintains its groove 57 inregister with the spherical elements 51. This enables the sphericalelements 51 to penetrate into the groove 57 whereby the bevel gear 48 isdisengaged from the hollow shaft 47. The upper end of the hollow shaft47 carries a disk 58 provided with an eccentric pin 59 for a connectingrod 60 which constitutes a mobile output element of the transmission forthe pneumatic impeller 61, 62 and is coupled to the cylinder 61 by a pin60a. The hollow shaft 47 is rotatable in a first antifriction bearing 49provided therefor in the portion 3b of the rear housing section 3 belowthe disk 58, and in a second antifriction bearing 50 installed in thehousing section 3 above the bevel gear 48. The shaft 55 for theeccentric pin 56 extends from the housing section 3 and is provided witha handle (not shown) similar to the handle 26 of FIG. 2 which enablesthe operator to engage or disengage the positive clutch between the disk58 and the bevel gear 46.

The piston 62 of the pneumatic impeller for the tool holder 37 isreceived in the cylinder 61 with minimal clearance. The hollow shaft 14can rotate about the cylinder 61.

The operation is as follows:

When the parts of the multi-speed transmission 9-16 for rotating thetool holder 37 at several speeds assume the positions shown in FIGS. 1and 2, the torque receiving teeth 18 of the hollow shaft 14 are locatedin the space 19 so that the gears 15 and 16 can be rotated by theelectric motor 4 but cannot drive the hollow shaft 14. Thus, thetransmission is in its neutral position and the projection 45 of theblocking shaft 44 can be moved into engagement with the adjacent teeth43 of the collar 42 so as to prevent rotation of the tool holder 37 andsleeve 36. By moving the eccentric pin 56 of the shaft 55 to the angularposition shown in FIG. 1, the operator engages the positiveclutchincluding the spherical elements 51 so that the bevel gear 48 can drivethe hollow shaft 47 and the disk 58. Consequently, when the motor 4 ison, the connecting rod 60 reciprocates the cylinder 61 and the piston 62transmits recurrent axial impulses to the shank 37a so that the tip of atool which is removably mounted in the holder 37 can be driven into aworkpiece, such as a block of concrete or rock.

If the operator thereupon decides to set the tool holder 37 in rotarymotion, the projection 45 is first disengaged from the collar 42 and theshaft 24 for the eccentric pin 25 is rotated in a clockwise direction,as

viewed in FIG. 3, whereby the pin 25 flexes the adja-- cent prong 23b ofthe leaf spring 23. The leaf spring 23 tends to move the shifter fork 17along the guide rod 22 so as to move the gears 15 and 16 in a directionto the right, as viewed in FIG. 3, and to thereby engage the torquereceiving teeth 18 of the hollow shaft 14 with the torque transmittingteeth 20 of the larger gear 15 which meshes with the smaller gear 12 ofthe intermediate shaft 10. The hollow shaft 14 is then rotated by thepinion 9, gear 11, shaft 10, gear 12, and gear 15 and drives the sleeve36 by way of the spherical elements 30 of the safety clutch. The balls38 rotate the shank 37a but the shank remains free to move axially underthe action of the piston 62 and counter to such action when theconnecting rod 60 retracts the cylinder 61. The shank 37a movesrearwardly when the cylinder 61 moves rearwardly because the operatorpushes the housing forwardly by way of the spade handle 3a.

If the material of the workpiece into which the tool penetrates isextremely hard, for example, if the material is concrete or rock, it canhappen that the tool holder 37 offers excessive resistance to rotationwith the hollow shaft 14. The safety clutch including the sphericalelements 30 then disengages the sleeve 36 from the hollow shaft 14 sothat the shaft 14 can rotate with the gear 15 while the sleeve 36 andthe tool holder 37 cease to rotate but the tool holder 37 remains freeto move axially. The pressure ring 31 of the safety clutch offers arelatively high resistance to axial movement in a direction toward theretainer 33 as long as the spherical elements 30 are engaged by itsinner conical surface 34; however, once the resistance which the shank37a offers to rotation increases to such an extent that the sphericalelements 30 are partially expelled from the flutes 35 of the sleeves 36,they can rapidly travel along the outer'conical surface 34a to thusinsure that the safety clutch is disengaged practically instantaneouslyorabruptly. This is desirable in order to avoid damage to or excessivewear upon the parts of the power tool. If desired, the retainer 33 canbe adjusted axially of the hollow shaft 14 to thereby select the exactresistance which the sleeve 36 must offer to rotation before the safetyclutch is disengaged. The spherical elements 30 are urged radiallyoutwardly by the axially parallel ribs which separate the flutes 35 ofthe sleeve 36 from each other.

An important advantage of the leaf spring 23 shown in FIG. 3 is that itenables the torque transmitting teeth or 21 of the gear 15 or 16 to moveinto mesh with the torque receiving teeth 18 of the hollow shaft 14 assoon as the teeth 18 move into register with the spaces between theteeth 20 or 21. Thus, when the shaft 24 is rotated clockwise orcounterclockwise, as viewed in FIG. 3, at a time when the teeth 18 donot register with the spaces between the teeth 20 or 21, thecorresponding prong 23b or 23a of the leaf spring 23 is deformed so thatthe spring 23 stores energy and is ready to propel the gears 15 and 16axially of the hollow shaft 14 as soon as the spaces between the teeth20 or 21 move into register with the teeth 18. It will be recalled thatthe gears 15 and 16 are rotated continuously by the gears 12 and 13whenever the motor 4 is on.

If the tool holder 37 is to be rotated at the higher of two speeds, thegears 15 and 16 are shifted in a direction to the left, as viewed inFIG. 1, so that .the torque receiving teeth 18 of the hollow shaft 14move into mesh with the torque transmitting teeth 21 of the smaller gear16 which is driven by the larger gear 13 of the intermediate shaft 10.The shifting from higher to lower speed ratio, or vice versa, as well asfrom higher lower speed ratio to neutral position of the multi-speedtransmission 9-16 can be effected while the motor 4 is on. It will benoted that the provision of the two control devices including the shafts55 and 24 enables the operator to impart to the tool holder 37 axialimpulses while the tool holder rotates or while thetool holder is heldagainst rotation. Inversely, the operator can decide to disengage thepositive clutch between the bevel gear 46 and disk 58 of thetransmission for the pneumatic impeller 61, 62 and to thereupon drivethe tool holder 37 at the higher or lower speed so that the tool holder37 rotates but does not perform any axial movements. The positive clutchcan be disengaged while the hollow shaft 14 rotates at a selected speed.The tool holder 37 can accept a variety of different tools as well oneor more adapters which enable it to accept further types or sizes oftools. This enhances the versatility of the power tool.

The portable power tool of FIG. 4 employs a modified positive clutchbetween the input element 60 and the output element 60 of thetransmission for the pneumatic impeller including the cylinder 61 andpiston 62. This clutch is a claw clutch having an annulus of claws 67 onthe right-hand (rear end face of the input element 66 (which correspondsto the gear 11 of FIG. 1 but is movable axially of the intermediateshaft 65) and an annulus of complementary claws 68 on the left-hand endface of a bevel gear 69 which is rotatable on the intermediate shaft 65.The control means for engaging and disengaging the claws 67 and 68comprises a suitable shifter having a handgrip portion 66a (indicated bybroken lines) which extends from the housing of the power tool so thatit can be manipulated by hand. The bevel gear 69 is in permanent meshwith a bevel gear 69a which replaces the disk 58 of FIG. 1 and carriesthe pin 59 for the output element or connecting rod 60. The bevel gear69a is secured to a shaft 69b which is rotatable in antifrictionbearings provided therefor in the rear housing section 3.

The intermediate shaft 65 is rotatable in two axially spacedantifriction bearings 65a, 65b having rollershaped rollings elements.

The construction of the multi-speed transmission which rotates the toolholder for the tool T is identical with that of the multi-speedtransmission 9-16 of FIG. 1. The control means 66a can be manipulated toengage or disengage the positive claw clutch 67, 68 while themulti-speed transmission is in neutral position or while the multi-speedtransmission rotates the tool T at a selected speed. Analogously, thespeed ratio of the multi-speed transmission can be changed or themultispeed transmission can be shifted to neutral while the claws 67engage the claws 68.

FIG. 5 illustrates a portion of a third portable power tool whichcomprises modified control means for changing the speed ratio of themulti-speed transmission for the tool holder. The intermediate shaft 10carries two gears 12, 13 which'respectively mesh with gears 72 and 73,both freely rotatable on the hollow shaft 14. The gears 72, 73 arerespectively analogous to the gears 15, 16 of FIGS. 1 and 3. Instead ofbeing rotatably mounted directly on the hollow shaft 14, the gears 72and 73 are mounted on a cylindrical or sleevelike shifter 74 which ismovable axially of the shaft 14. The shifter 74 is provided with anannulus of external torque receiving teeth or projections 75 and servesto rotate the shaft 14'. The teeth 75 are functional equivalents ofteeth 18 on the shaft 14 of FIG. 1 and can be moved into mesh withinternal torque transmitting teeth or projections 76 of the gear 72 orwith internal torque transmitting teeth or projections of the gear 73,depending upon whether the user of the power tool wishes to drive thetool holder at a lower or higher speed. The control means for moving theshifter 74 axially of the shaft 14' is preferably similar to oridentical with the control means 17, 23, 24, 25, 26 of FIGS. 2 and 3.The gears 72, 73 are held against axial movement. The internal teeth 76and 77 of the gears 72, 73 are separated from each other by aring-shaped space 78 which is wide enough to accommodate the externalteeth 75 of the shifter 74 when the user of the power tool wishes tomaintain the multi-speed transmission for the tool holder in neutralposition.

The portable power tool of FIG. 6 comprises a third embodiment of adisengageable positive clutch between the input element 46 and theoutput element 60 of the transmission for the pneumatic impeller 61, 62.

the clutch comprises a shaft 81 which carries at its upper end a disk 82for the eccentric pin 59 and can receive torque from a sleeve-likeclutch element 83 which is axially movably mounted thereon and is biaseddownwardly, as viewed in FIG. 6, by a helical spring 81a. The latterreacts against the inner race of an antifriction bearing 81b for theupper portion of the shaft 81. The lower end face of the clutch element83 carries an annulus of claws 84 which can be moved into mesh withsimilar claws 85 provided on the upper end face of a bevel gear 86 whichis in permanent mesh with the bevel gear 46. The latter is secured tothe intermediate shaft 10. The clutch element 83 can be shifted axiallyby control means similar to that including the parts 17, 23, 24, 25, 26shown in FIGS. 2 and 3.

The construction of the multi-speed transmission for the tool T isidentical with that of the multi-speed transmission shown in FIGS. 1 to3.

FIG. 7 illustrates a portable power tool which embodies a modifiedsafety clutch for disengaging the tool holder 37 from the prime mover(not shown) when the tool holder offers excessive resistance to rotationwith the hollow shaft 14". The hollow shaft 14 is provided with axiallyparallel slots or openings 89 for rollershaped torque transmittingclutch elements 90 (only one shown) which extends into the adjacentflutes 35 of the sleeves 36 under the action of the spring 32. Thepressure ring 31 of FIG. 1 is replaced by two pressure rings 91, 92 theformer of which abuts against a split ring 93 in a peripheral groove ofthe shaft 14". The rear pressure'ring 92 is biased toward the pressurering 91 by the spring 32. The axes of the roller-shaped elements 90 areparallel with the axis of the hollow shaft 14". Each of the pressurerings 91, 92 is provided with a conical surface (91a, 92a) into which aportion of each element 90 normally extends. The pressure ring 92 yieldsand moves in a direction to the right to further stress the spring 32when the sleeve 36 offers excessive resistance to rotation with theshaft 14". This allows the shaft 14 to rotate relative to the sleeve 36and tool holder 37 but the parts of the power tool cannot be damagedbecause the tool ceases to rotate.

in all other respects, the construction of the power tool of FIG. 7 isidentical with that of one of the power tools shown in FIG. 1, '4, or 6.i

It is clear that the features shown in FIGS. 4 and 7, 5 and 7 or 6 and 7can be incorporated in a single power tool.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of our contribution to the art and, therefore, suchadaptations should and are intended to be comprehended within themeaning and range of equivalence of the claims. i

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

1. A portable power tool, particularly a combined electric impact wrenchand chipping hammer, comprising a housing; a prime mover mounted in saidhousing and having a rotary output member; a tool holder rotatably andaxially movably mounted in said housing; impeller means mounted in saidhousing and actuatable to transmit to said tool holder recurring axialimpulses; first transmission means mounted in said housing and having aninput element receiving torque from said output member, a mobile outputelement for actuating said impeller means, and clutch means for movingsaid output element in response to rotation of said input element; firstcontrol means for disengaging said clutch means at the will of theoperator; multispeed second transmission means mounted in said housingbetween said tool holder and said output member and having a pluralityof different speed ratios and a neutral position; and second controlmeans actuatable independently of said first control means to select thespeed ratio or the neutral position of said second transmission means sothat said tool holder is movable axially by said impeller means whilesaid second transmission means is in said neutral position or drivessaid tool holder at a selected speed, and that said output element ofsaid first transmission means is idle while said second transmissionmeans rotates said tool holder at a selected speed. rotates said toolholder at a selected speed.

2. A power tool as defined in claim 1, wherein said impeller meanscomprises a pneumatic cylinder and piston unit including a cylinderwhich is reciprocable by said output element of said first transmissionmeans and a piston which is reciprocable in said cylinder and isarranged to impart said impulses to said tool holder.

3. A power tool as defined in claim 1, wherein said second transmissionmeans comprises a two-speed transmission.

4. A power tool as defined in claim 1, further comprising a safetyclutch installed between said second transmission means and said toolholder and arranged to disconnect said tool holder from said secondtransmission means when said tool holder offers a predeterminedresistance to rotation.

5. A power tool as defined in claim I, wherein said prime movercomprises an electric motor and said clutch means comprises a positiveclutch.

6. A power tool as defined in claim 5, wherein said positive clutchcomprises a hollow shaft arranged to transmit torque to said outputelement and having at least one opening, a torque transmitting elementprovided in said opening and movable between a first position in whichit partly extends from said hollow shaft and is driven by said inputelement and a second position in the interior of said hollow shaft, anda displacing member movable in said shaft axially between an operativeposition in which said displacing member maintains said torquetransmitting element in said first position and an inoperative positionin which said torque transmitting element is free to assume said secondposition, said first control means being arranged to move saiddisplacing member between said operative and inoperative positions.

7. A power tool as defined in claim 6, wherein said torque transmittingelement is a sphere and said input element includes a gear having aninternal recess which receives a portion of said sphere in said firstposition of said sphere, said displacing member comprising a bolt havinga groove which receives a portion of said sphere in said second positionof said sphere when said bolt assumes said inoperative position.

8. A power tool as defined in claim 7, wherein said positive clutchfurther comprises biasing means or permanently urging said bolt to oneof said positions thereof and said first control means comprises aneccentric actuatable to move said bolt to the other of said positionsagainst the opposition of said biasing means.

9. A power tool as defined in claim 5, wherein said positive clutchcomprises a first annulus of claws driven by said input element and asecond annulus of complementary claws arranged to move said outputelement, said first control means comprising means for moving one ofsaid annuli of claws toward and away from the other annulus to therebyplace the claws of said first annulus into and out of mesh with theclaws of said second annulus.

10. A power tool as defined in claim 9, wherein said input elementcomprises a first gear which receives torque from said prime mover andsaid output element comprises or is movable by a second gear which iscoaxial with said first gear one of said gears being movable axiallytoward and away from the other of said .gears and said first and secondannuli of claws being respectively provided on said first and secondgears and being located between said gears.

11. A power tool as defined in claim 5, wherein said positive clutchcomprises a shaft which is arranged to drive said output element, a gearrotatably mounted on said shaft and receiving torque from said outputmember of said prime mover, a clutch element rotatable with and movableaxially of said shaft toward and away from said gear, a first annulus ofclaws provided on said gear and facing said clutch element, and a secondannulus of complementary claws provided on said clutch element andfacing said gear, said first control means comprising means for movingsaid clutch element toward and away from said gear to thereby move saidsecond annulus of claws into and from mesh with said first annulus ofclaws.

12. A power tool as defined in claim 1, wherein said second transmissionmeans comprises a two-speed transmission including an intermediate shaftdriven by said output member of said prime mover, a second shaftarranged to transmit torque to said tool holder, coaxial first andsecond gears rotatably mounted on said second shaft and being driven bysaid intermediate shaft at different speeds and respectively havingfirst and second torque transmitting portions, and torque receivingmeans provided on said second shaft, said gears being movable axially ofsaid second shaft and said second control means comprising shifter meansactuatable to move said first or second torque transmit ting portioninto engagement with said torque receiving means.

13. A power tool as defined in claim 12, wherein said second controlmeans further comprises a manually operable eccentric for moving saidgears axially by way of said shifter means.

14. A power tool as defined in claim 13, wherein said second controlmeans further comprises resilient means interposed between saideccentric and said shifter means so that said shifter means can movesaid gears axially when one of said first and second torque transmittingportions is ready to move into engagement with said torque receivingmeans of said second shaft.

15. A power tool as defined in claim 1, wherein said second transmissionmeans comprises 'a' two-speed transmission including a first shaftdriven by said output member of said prime mover, a second shaftarranged to drive said tool holder, a sleeve-like shifter movableaxially of and rotatable with-said second shaft,

first and-second gears driven by said first shaft at different speedsand surrounding said shifter, first and second torque transmittingportions respectively provided on said first and second gears, andtorque receiving means provided on said shifter, said second controlmeans comprising means for moving said shifter axially betweena firstposition in which said torque receiving means receives torque from saidfirst torque transmitting portion, a second portion in which said torquereceiving means receives torque from said second torque transmittingportion, and a third portion in which said torque receiving means isdisengaged from said first and second torque transmitting portions.

16. A power tool as defined in claim 15, wherein said second controlmeans comprises a manually operable eccentric for moving said shifteraxially of said second shaft.

17. A power tool as defined in claim 16, wherein said second controlmeans further comprises resilient means interposed between said shifterand said eccentric so that said shifter can move axially when saidmotion receiving means thereof registers with one of said first andsecond troque transmitting portions.

18. A power tool as defined in claim 1, further comprising blockingmeans actuatable to prevent rotation of said tool holder.

19. A power tool as defined in claim 18, further comprising a sleeverotatable with said tool holder and having at least one external axiallyparallel groove, said blocking means comprising a shaft rotatable byhand and having a projection movable into and from said groove, the axisof said shaft being inclined relative to the axis of said sleeve.

20. A power tool as defined in claim 1, further comprising a safetyclutch installed between said second transmission means and said toolholder and arranged to disconnect said tool holder from said secondtransmission means when said tool holder offers a predeterminedresistance to rotation, said safety clutch comprising at least onetorque transmitting element movable between an operative position inwhich said second transmission means trasmits torque to said tool holderand an inoperative position in which said tool holder, is disconnectedfrom said second transmission means.

21. A power tool as defined in claim 20, wherein said safety clutchfurther comprises a sleeve arranged to rotate said tool holder andhaving a flute which normally receives a first portion of said torquetransmitting element in said operative position thereof, said secondtransmission comprising a hollow shaft surrounding said flute and havinga radial opening receiving a second portion of said torque transmittingelement in said operative position thereof, said safety clutch furthercomprising a pressure transmitting member arranged to yieldably urgesaid torque transmitting element to said operative position and topermit said torque transmitting element to move to said inoperativeposition, in which latter position said first portion of said torquetransmitting element is received in said opening, in response to saidpredetermined resistance of said tool holder to rotation with saidshaft.

22. A power tool as defined in claim 21, wherein said pressuretransmitting member is a ring which surrounds and is axially movable onsaid hollow shaft, said torque transmitting element having a thirdportion which extends radially beyond said opening and is in abutment 13with said ring in said operative position thereof, said safety clutchfurther comprising resilient means for biasing said ring against saidtorque transmitting element.

23. A power tool as defined in claim 22, wherein said ring has at leastone outwardly flaring conical surface which is engaged by said torquetransmitting element in said operative position thereof.

24. A power tool as defined in claim 22, wherein said pressure ring hasa first radially outwardly flaring conical surface which contacts saidtorque transmitting element in said operative position thereof and asecond torque transmitting element is a roller.

1. A portable power tool, particularly a combined electric impact wrenchand chipping hammer, comprising a housing; a prime mover mounted in saidhousing and having a rotary output member; a tool holder rotatably andaxially movably mounted in said housing; impeller means mounted in saidhousing and actuatable to transmit to said tool holder recurring axialimpulses; first transmission means mounted in said housing and having aninput element receiving torque from said output member, a mobile outputelement for actuating said impeller means, and clutch means for movingsaid output element in response to rotation of said input element; firstcontrol means for disengaging said clutch means at the will of theoperator; multispeed second transmission means mounted in said housingbetween said tool holder and said output member and having a pluralityof different speed ratios and a neutral position; and second controlmeans actuatable independently of said first control means to select thespeed ratio or the neutral position of said second transmission means sothat said tool holder is movable axially by said impeller means whilesaid second transmission means is in said neutral position or drivessaid tool holder at a selected speed, and that said output element ofsaid first transmission means is idle while said second transmissionmeans rotates said tool holder at a selected speed. rotates said toolholder at a selected speed.
 2. A power tool as defined in claim 1,wherein said impeller means comprises a pneumatic cylinder and pistonunit including a cylinder which is reciprocable by said output elementof said first transmission means and a piston which is reciprocable insaid cylinder and is arranged to impart said impulses to said toolholder.
 3. A power tool as defined in claim 1, wherein said secondtransmission means comprises a two-speed transmission.
 4. A power toolas defined in claim 1, further comprising a safety clutch installedbetween said second transmission means and said tool holder and arrangedto disconnect said tool holder from said second transmission means whensaid tool holder offers a predetermined resistance to rotation.
 5. Apower tool as defined in claim 1, wherein said prime mover comprises anelectric motor and said clutch means comprises a positive clutch.
 6. Apower tool as defined in claim 5, wherein said positive clutch comprisesa hollow shaft arranged to transmit torque to said output element andhaving at least one opening, a torque transmitting element provided insaid opening and movable between a first position in which it partlyextends from said hollow shaft and is driven by said input element and asecond position in the interior of said hollow shaft, and a displacingmember movable in said shaft axially between an operative positIon inwhich said displacing member maintains said torque transmitting elementin said first position and an inoperative position in which said torquetransmitting element is free to assume said second position, said firstcontrol means being arranged to move said displacing member between saidoperative and inoperative positions.
 7. A power tool as defined in claim6, wherein said torque transmitting element is a sphere and said inputelement includes a gear having an internal recess which receives aportion of said sphere in said first position of said sphere, saiddisplacing member comprising a bolt having a groove which receives aportion of said sphere in said second position of said sphere when saidbolt assumes said inoperative position.
 8. A power tool as defined inclaim 7, wherein said positive clutch further comprises biasing means orpermanently urging said bolt to one of said positions thereof and saidfirst control means comprises an eccentric actuatable to move said boltto the other of said positions against the opposition of said biasingmeans.
 9. A power tool as defined in claim 5, wherein said positiveclutch comprises a first annulus of claws driven by said input elementand a second annulus of complementary claws arranged to move said outputelement, said first control means comprising means for moving one ofsaid annuli of claws toward and away from the other annulus to therebyplace the claws of said first annulus into and out of mesh with theclaws of said second annulus.
 10. A power tool as defined in claim 9,wherein said input element comprises a first gear which receives torquefrom said prime mover and said output element comprises or is movable bya second gear which is coaxial with said first gear one of said gearsbeing movable axially toward and away from the other of said gears andsaid first and second annuli of claws being respectively provided onsaid first and second gears and being located between said gears.
 11. Apower tool as defined in claim 5, wherein said positive clutch comprisesa shaft which is arranged to drive said output element, a gear rotatablymounted on said shaft and receiving torque from said output member ofsaid prime mover, a clutch element rotatable with and movable axially ofsaid shaft toward and away from said gear, a first annulus of clawsprovided on said gear and facing said clutch element, and a secondannulus of complementary claws provided on said clutch element andfacing said gear, said first control means comprising means for movingsaid clutch element toward and away from said gear to thereby move saidsecond annulus of claws into and from mesh with said first annulus ofclaws.
 12. A power tool as defined in claim 1, wherein said secondtransmission means comprises a two-speed transmission including anintermediate shaft driven by said output member of said prime mover, asecond shaft arranged to transmit torque to said tool holder, coaxialfirst and second gears rotatably mounted on said second shaft and beingdriven by said intermediate shaft at different speeds and respectivelyhaving first and second torque transmitting portions, and torquereceiving means provided on said second shaft, said gears being movableaxially of said second shaft and said second control means comprisingshifter means actuatable to move said first or second torquetransmitting portion into engagement with said torque receiving means.13. A power tool as defined in claim 12, wherein said second controlmeans further comprises a manually operable eccentric for moving saidgears axially by way of said shifter means.
 14. A power tool as definedin claim 13, wherein said second control means further comprisesresilient means interposed between said eccentric and said shifter meansso that said shifter means can move said gears axially when one of saidfirst and second torque transmitting portions is ready to move intoengagement with said torque receiving means of said second shaft.
 15. Apower tool as defined in claim 1, wherein said second transmission meanscomprises a two-speed transmission including a first shaft driven bysaid output member of said prime mover, a second shaft arranged to drivesaid tool holder, a sleeve-like shifter movable axially of and rotatablewith said second shaft, first and second gears driven by said firstshaft at different speeds and surrounding said shifter, first and secondtorque transmitting portions respectively provided on said first andsecond gears, and torque receiving means provided on said shifter, saidsecond control means comprising means for moving said shifter axiallybetween a first position in which said torque receiving means receivestorque from said first torque transmitting portion, a second portion inwhich said torque receiving means receives torque from said secondtorque transmitting portion, and a third portion in which said torquereceiving means is disengaged from said first and second torquetransmitting portions.
 16. A power tool as defined in claim 15, whereinsaid second control means comprises a manually operable eccentric formoving said shifter axially of said second shaft.
 17. A power tool asdefined in claim 16, wherein said second control means further comprisesresilient means interposed between said shifter and said eccentric sothat said shifter can move axially when said motion receiving meansthereof registers with one of said first and second troque transmittingportions.
 18. A power tool as defined in claim 1, further comprisingblocking means actuatable to prevent rotation of said tool holder.
 19. Apower tool as defined in claim 18, further comprising a sleeve rotatablewith said tool holder and having at least one external axially parallelgroove, said blocking means comprising a shaft rotatable by hand andhaving a projection movable into and from said groove, the axis of saidshaft being inclined relative to the axis of said sleeve.
 20. A powertool as defined in claim 1, further comprising a safety clutch installedbetween said second transmission means and said tool holder and arrangedto disconnect said tool holder from said second transmission means whensaid tool holder offers a predetermined resistance to rotation, saidsafety clutch comprising at least one torque transmitting elementmovable between an operative position in which said second transmissionmeans trasmits torque to said tool holder and an inoperative position inwhich said tool holder is disconnected from said second transmissionmeans.
 21. A power tool as defined in claim 20, wherein said safetyclutch further comprises a sleeve arranged to rotate said tool holderand having a flute which normally receives a first portion of saidtorque transmitting element in said operative position thereof, saidsecond transmission comprising a hollow shaft surrounding said flute andhaving a radial opening receiving a second portion of said torquetransmitting element in said operative position thereof, said safetyclutch further comprising a pressure transmitting member arranged toyieldably urge said torque transmitting element to said operativeposition and to permit said torque transmitting element to move to saidinoperative position, in which latter position said first portion ofsaid torque transmitting element is received in said opening, inresponse to said predetermined resistance of said tool holder torotation with said shaft.
 22. A power tool as defined in claim 21,wherein said pressure transmitting member is a ring which surrounds andis axially movable on said hollow shaft, said torque transmittingelement having a third portion which extends radially beyond saidopening and is in abutment with said ring in said operative positionthereof, said safety clutch further comprising resilient means forbiasing said ring against said torque transmitting element.
 23. A powertool as defined in claim 22, wherein said ring has at least oneoutwardly flaring conical surface which is engagEd by said torquetransmitting element in said operative position thereof.
 24. A powertool as defined in claim 22, wherein said pressure ring has a firstradially outwardly flaring conical surface which contacts said torquetransmitting element in said operative position thereof and a secondradially outwardly flaring conical surface which is engaged by saidtorque transmitting element in said inoperative position thereof, saidfirst and second conical surfaces respectively making with the axis ofsaid hollow shaft a relatively small and a relatively large acute angle.25. A power tool as defined in claim 22, wherein said torquetransmitting element is a sphere.
 26. A power tool as defined in claim22, wherein said torque transmitting element is a roller.